This invention relates, in general, to optical sensors, and more specifically, to passive multi-conical beam optical detecting systems.
Long-wavelength-infrared (LWIR) passive optical systems for conical beam target detection, such as the system described in U.S. Pat. No. 4,809,611 issued Mar. 7, 1989 to Roy Esplin, result in curved focal surfaces. To obtain an optical conical field-of-view (FOV) from the curved focal surfaces, annular-ring-detector-arrays (ARDA) are placed at the focal surface of such optical systems. The ARDA are then positioned and sized to achieve the desired cone geometry. For a 360 degree azimuthal conical FOV, the ARDA requires four (4) optical system quadrants, each with near 90 degree FOV arcs, as described in the '611 patent.
When a passive sensor requires two or more conical FOV, the ARDAs for each FOV must be added to the focal surface in separate planes. Since detector arrays can only be grown on flat wafer surfaces, each ARDA must be fabricated in separate areas on the wafer substrate and cut from the wafer. The ARDAs are then each individually positioned in a precise manner at the focal surface of the optical system. This process is costly and time consuming, and does not lend itself well to large scale production techniques. Ideally, all ARDA required for a 360 azimuth could be placed on a single wafer.